1. Field of the Invention
This invention relates generally to electrical connectors and particularly to a PCMCIA electrical connector of a type circumjacent front and side edges of a printed circuit board.
2. Description of the Related Art
Electrical connectors for printed circuit boards have been known for many years wherein the connectors have terminals with a portion often referred to as a "solder tail" extending rearwardly from a contact in an insulating housing for insertion into holes in a printed circuit board. Miniaturization of such connectors led to the development of surface mount connectors having terminals with solder tails configured for positioning against and connection to conductive pads or circuit traces on the surface of the board. That the solder tails are mounted to a surface of the board is the reason for terming this type of connector "surface mount".
A wide variety of surface mount connectors have been developed, some including socket-type terminals with receptacle contacts for mating with pins of a complementary mating male connector, and others containing terminal pin headers which mount a plurality of terminals with contact pins projecting therefrom for mating with socket-type terminals. Representative surface mount connectors are described in U.S. Pat. Nos. 5,346,404, 5,316,489, 5,269,694, 5,238,412, 5,230,633, 5,213,515, 5,020,999, and 4,717,218.
Typically in a surface mount terminal connector of either the socket or pin header terminal type, the receptacle contacts or contact pins typically project from the connector in spaced apart horizontal rows parallel to the board, whereas all the solder tails are in a single horizontal plane for connection to the planar array of conductive pads on the one side of the board. The solder tails of the terminals are typically arranged in a single row or coplanar rows for automated interconnection to the conductive pads on the circuit board. In fact, automated assembly is a critical design consideration with respect to surface mount connectors. As much of the assembly operation as can be accomplished through the use of robotics is desirable so that manufacturing costs can be kept as low as possible. Two aspects of automated electrical connector assembly are especially relevant, the first relating to the physical placement of the connector in contact with the printed circuit board, and the second relating to the soldering step.
The connector housing is usually mounted to the surface of the printed circuit board in surface mount connectors along with the solder tails. Such surface mounted connector housings do not lend themselves readily to automated alignment and engagement with the circuit board. They therefore usually have to be placed on the board by hand to ensure proper positioning for soldering the leads in place. In this case the connector could become disoriented or fall off the printed circuit board before or during the reflow soldering operation, and especially if the connector and printed circuit board are automatically conveyed to the reflow soldering station.
In reflow soldering, after an appropriate application of solder cream and flux to the conductive pads and physical positioning of the solder tails of the connector thereon, the circuit board is heated, often by means of exposure to radiation in the form of infrared or laser beam energy, to cause a melting or reflow of the solder. The board is then cooled to establish the solder joints between the solder tails and the conductive pads to provide electrical interconnection.
Connectors of the type discussed to this point are used in the manufacture of internal hard disk drive assemblies enclosed in a unitary enclosure having a cover and a base plate. The hard drives include at least one rotating disk carrying a storage medium thereon, means for rotating the disk, and an movable actuator arm carrying a read/write head for retrieving and/or recording information on the storage medium. In addition, a printed circuit board containing the control circuitry is often mounted in the enclosure. The disk spindle motor and actuator are most often mounted to the base plate and electrically connected to the printed circuit board which in turn is electrically connected via a surface mount electrical connector in the manner above described for external interface to the central processing unit of a computer. The cover, together with the base plate, defines an environmental enclosure for the disk drive.
Developments in personal, portable, and laptop computers have prompted reductions in the size and increases in memory capacity of hard disk drives which heretofore were invisible to the end user. As portability has become a more important consideration, an industrial dimensional and interface standard for removable components of a computer system was developed. This standard is known as the Personal Computer Memory Card International Association (PCMCIA) standard. PCMCIA memory cards, which include miniature hard disk drive, are themselves portable, interchangeable between computers, and can be removed and reinserted by the end user on a regular basis. Therefore PCMCIA disk drives need a robustness that heretofore has not been required.
Conventional PCMCIA connectors now in use in these miniature hard disk drive assemblies are fastened to the associated printed circuit board in the assembly solely by the solder tails of the connector soldered to the termination pads of the printed circuit board. The printed circuit board is, in turn, fastened to the base plate of the hard disk drive enclosure. Since these PCMCIA dimensioned connector assemblies are repeatedly connected and disconnected from the host computer, this regular handling creates frequent flexure of these solder joints. This lead flexure can result in cracking of the solder joints and ultimately result in connection failure. The result of such failures is a useless component such as a memory card or hard disk drive.
Lead flexure is not a new problem. The above-referenced United States Patents typify solutions to the problem of lead flexure with respect to surface mount connectors. While numerous attempts to address lead flexure in electrical connectors in general have been made, the existing solutions relate to connectors having housings which themselves are fastened to the surface of the printed circuit board. With such a mounting, external forces on the connector, torsional or otherwise, will be transferred directly to the solder joints.
The problem of lead flexure is especially acute with respect to PCMCIA devices, i.e., devices in compliance with the PCMCIA standards as the conventional PCMCIA connector is supported entirely by the electrical solder joints between the connector solder tails and the conductive pads on the printed circuit board. As previously mentioned, the solder joints are repeatedly strained by the coupling and uncoupling of the mating connectors, bringing about connection failure. There is therefore a need for an electrical connector assembly for use in PCMCIA standard applications, wherein the connector housing can engage a printed circuit board and can be retained on the circuit board before and during reflow soldering, thereby reducing manufacturing costs. There is also a need for the connector to engage the circuit board in such a way that any force applied to the connector which is not isolated is strain relieved to the printed circuit board and not to the solder joints. Finally, there is also a need for a connector mounting design which also isolates the connector from transmitting externally applied forces to the printed circuit board.